#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n, m; cin >> n >> m;
    vector<int>cnt(n+1);
    for(int i = 0; i < m; i++)
    {
        int a, b; cin >> a >> b;
        cnt[a]++, cnt[b]--;
    }

    int ans = 0;
    bool b = false;
    for(int i = 1; i <= n; i++)
    {
        cnt[i] += cnt[i-1];
        if(!b && cnt[i] == 0)
        {
            ans++;
            b = true;
        }
        if(cnt[i] != 0 && b)b = false;
    }
    cout << ans;
    return 0;
}